Variable focus spectacles

ABSTRACT

Variable focus spectacles which comprise i) a focus module that includes two variable focus lens sections, said sections each including a first fixed plastic lens and an adjustable focus liquid lens, and ii) a second fixed plastic lens that preferably includes most or all of the optical power needed by the intended wearer to correct his/her distance vision. The second fixed plastic lens is preferably attached to the focus module by magnetic attraction.

BACKGROUND OF THE INVENTION

The invention described herein is a new type of variable focusspectacles for presbyopes. As people age, they gradually lose theability to focus their eyes at various distances. After about the age of40, the loss of “accommodation” (as the adjustable focusing ability ofhumans is called) generally becomes so severe that for almost all peopleit is not possible to focus both on distant objects and on objects atreading distance, even after distance vision has been corrected. Specialtypes of spectacles have been developed to address this problem:bifocals, trifocals and “PALs” (Progressive Addition Lens). But thesetypes of spectacles have serious deficiencies. They require the user tolook through different regions of the lens when trying to focus onobjects at different distances from the user. For example, a PAL usermust look through the upper portion of the lens when looking at adistant object, and through a very small region in the lower center ofthe lens when reading a book. Similarly, bifocal users also must lookthrough a small region in the lower portion of the lens to read. Suchrestrictions are unsatisfactory in many circumstances.

SUMMARY OF THE INVENTION

Spectacles made in accordance with the presently preferred embodiment ofthe invention are comprised of

i) a “focus module” that includes two variable lens sections, each ofwhich is constructed to provide a user adjustable optical power, and

ii) a pair of preferably detachable prescription lenses placed in frontof the variable lens sections, each of which provides an additionalfixed optical power.

The prescription lenses in front of the variable lenses are preferablydetachable and may be retained by magnets. Alternatively, they may beretained by other means, such as spring clips or other means. They arecalled “prescription” lenses here because they preferably include mostor all of the optical correction needed by the intended user to viewdistant objects clearly (the user's “distance prescription”). Thecorrection needed may involve spherical, cylindrical, and/or possiblyprismatic components.

One advantage of the present invention is that the prescription lensesmay be fabricated from standard off-the-shelf finished ophthalmic lensblanks. They may also, of course, be fabricated from semi-finishedblanks, or from other starting materials.

The optical powers of the variable lens sections may be adjusted by theuser (preferably both simultaneously) through use of an actuator whichis preferably contained within the bridge of the spectacles. Theadjustable lens sections provide a variable spherical “ADD” to enablethe user to focus on objects at various distances, for example at anydistance between infinity and reading distance. The combination of oneof the variable lens sections with a prescription lens in front issometimes referred to herein as a “lens unit”. The prescription lensesare sometimes called the “front” lenses, even though in someembodiments, as will be mentioned below, these lenses are not furthestaway from the user's eyes.

As will be further discussed below, each lens unit is comprised of threelenses (a front lens, a variable liquid lens, and a rear lens). In thepresently preferred embodiment of the invention, the front lensincorporates the intended user's distance prescription, including thespherical, cylindrical and prismatic components thereof, but if desired,portions (or possibly all) of the prescription could alternatively beincorporated in the rear lens. Also, the spherical component of theuser's prescription, or a portion thereof, could be embodied in thevariable liquid lens, if desired.

The focus module, which includes the rear lenses and the variable liquidlenses, contributes a predetermined range of variable spherical opticalpower to the total, for example zero to +3 diopters. If the front lensesincorporate all of the intended user's distance prescription, then whenthe focus module is adjusted to provide zero diopters of optical power,the intended user's eyes will be focused on distant objects. If thefocus module is adjusted to +3 diopters, the intended user will focus onan object ⅓ meters (about 13 inches) away from his or her eyes.

It will be appreciated that the focus module could alternatively beconstructed to provide ranges of optical power other than zero to +3diopters, for example +1 to +3.5 diopters. In that case, the frontlenses would preferably be fabricated to provide optical power which isless than the intended user's distance prescription by 1 diopter. Underthese conditions, when the focus module is set to provide +1 diopter ofoptical power, the net optical power of the system will be such that theintended user will be able to view distant objects clearly, and when thefocus module is set to provide +3.5 diopters, the spectacles as a wholewill be providing +2.5 diopters of optical power more than the intendeduser's distance prescription, and hence he or she will be able to seeclearly an object 1/2.5 meters (about 16 inches) away from his or hereyes.

In the description of the invention contained herein it is assumed, forsimplicity, that the user's two eyes are identical, hence only oneoptical power need be discussed to describe the invention. Personsskilled in the art will appreciate, however, that the opticalrequirements for the two eyes for many users will not be the same, andconsequently, the two lens units in spectacles for those persons willnot have the same optical characteristics.

The terms “front” and “rear”, as used in this document refer to thedirections away from and toward a wearer of the spectacles. Hence, the“rear” lens is the lens closest to the user's eyes. The various parts ofthe focus module are preferably fastened together by laser welding.Where explicitly shown, typical welds are indicated by solid blacktriangular areas in the drawings.

Obviously, a complete pair of spectacles normally includes some meansfor holding the spectacles in position on the intended user's face. Suchmeans could, for example, consist of temples attached to the focusmodule, or to the front lenses. The spectacles also preferably includenosepads. For clarity, these elements are not shown in the drawings.However, since appropriate temples and nosepads, as well as methods ofincorporating them on spectacles, are well known in the art, thosepersons familiar with the art will have no difficulty in including suchitems in completed spectacles.

The description and drawings herein refer to the focus module as havinga “rear” lens, with a liquid lens in front thereof (between the rearlens and the front lens). It will be appreciated that the same goals canbe achieved, according to the principles of the present invention, in analternate construction wherein the focus module is reversed. That is,where the liquid lens is the rearmost element (the film facing theuser's eyes), and where the “rear” lens is located between the liquidlens and the front lens. Such construction is intended to be coveredhereby as well as the preferred construction that is described indetail. Another alternate construction that is intended to be coveredhereby uses lens units and focus modules constructed as described above,except that they are constructed to be worn by a user with the “front”lens facing the user's face, and the “rear” lens facing outward, theliquid lens being in between.

A more complete understanding of the invention may be obtained byreference to the Description of the Invention below, together with theappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the invented spectacles, looking inward towarda where a wearer would be.

FIG. 2 is a partially exploded cross sectional view of one of the lensunits of the spectacles of FIG. 1 taken at 2-2 of FIG. 1 with the lensunit set for distance viewing.

FIG. 3 is a fragmentary detail of FIG. 2, the location of the fragmentis as denoted by the numeral “3” in FIG. 2, the lens unit being adjustedfor distance viewing.

FIG. 4 is a fragmentary detail similar to FIG. 3, except that the lensunit is set for close viewing, e.g., reading.

FIG. 5 is a fragmentary detail of FIG. 2, the location of the fragmentis as denoted by the numeral “5” in FIG. 2.

FIG. 6 is an oblique view of the leaf hinge used in connection with theillustrated embodiment of the invention.

FIG. 7 is an enlarged fragmentary section of a portion of arepresentative front lens, showing the detail of a presently preferredgroove into which the retaining magnets are inserted, the section beingtaken in a region where no magnets are located.

FIG. 8 is an enlarged fragmentary section of a portion of arepresentative front lens, showing the detail of a presently preferredgroove into which the retaining magnets are inserted, the section beingtaken in a region where a magnet is located.

FIG. 9 is a front view of a representative detachable front lens.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a front view of one embodiment of the invention. Two lensunits, 10 and 10′, are shown, held in relative position by a bridge 12.Within bridge 12, but not shown in detail, is an actuator for adjustingthe optical powers of the lens units. The actuator may, for example, beof the type described in U.S. Pat. No. 7,008,054, to which reference maybe made for more details. Accordingly, the disclosures of U.S. Pat. No.7,008,054 are incorporated herein by reference.

Inasmuch as the two lens units are mirror images of each other, only onewill be discussed.

The actuator may be coupled to the rear ring 20 of lens unit 10 throughlink 13. The link 13 (and its mirror mate on the left lens unit 10′ (notshown)) correspond to the links 35 and 36 in the above referencedpatent. The link 13 may be attached to the rear ring directly, or may beattached via a tab 11. As described in detail in U.S. Pat. No.7,008,054, adjustment of slider 30 (24 in the referenced patent) willcause the links 13 to move, which, in turn causes the rear ring 20 tomove in an arcuate manner, as will be discussed below.

Each lens unit includes three physically distinct lenses: a fixed powerfront lens 14, a fixed power rear lens 15, and a variable power liquidlens 16. The combination of the three lenses results in a lens unit thatis optically equivalent to a single lens such as is commonly used in anordinary pair of single vision spectacles, except that the lenses in theinvented spectacles have adjustable optical powers. In the preferredembodiment of the invention, the front lens is a “prescription” lens inthe sense that it is preferably made to include all or almost all of theintended user's distance prescription. This is not a required condition,however; the user's prescription can be realized in the front lens, inthe rear lens, or distributed among all three lenses of a lens unit, asmay be convenient. For example, the front lens could have no opticalpower, and the intended user's distance prescription could be entirelyin the rear and liquid lenses, or possibly entirely in the rear lens. Insome other case, the rear lens might have zero optical power, and insuch case the intended user's distance prescription would be entirely inthe front and liquid lenses.

FIG. 2 shows a cross sectional view of the right lens unit 10 where, forillustrative purposes, the front lens 14 is shown separated from thefocus module. A plurality of magnets are attached to the front lens 14,preferably in a groove 24 near the lens periphery (using an adhesive orother means). Four magnets are illustrated, but the number used inpractice will depend on the strength of the magnets and the amount ofholding force desired. As illustrated in FIG. 1, the magnets are visiblefrom the front of the lens unit. However, as will be discussed below, inthe presently preferred embodiment of the invention, the groove 24 ispreferably filled with an opaque plastic compound, and the magnets willtherefore be hidden; what is seen by an onlooker would be a circularstripe at the groove location.

The preferred magnet material is of the rare earth type, such assamarium cobalt or neodymium iron boron because their magneticproperties permit relatively high holding forces. Other magneticmaterials are, of course, also possible. The magnets are attracted tothe front ring (or rim) 19 of the focus module (which ring/rim ispreferably fabricated from ferromagnetic material, as for example, 17-4PH steel). The magnetic attraction thereby holds the front lens to thefocus module. This arrangement permits the front lenses to be removedfor cleaning, for replacement by sun lenses, or for other reasons.

FIG. 7 shows a fragmentary sectional view of a front lens 14, enlargedto show the detail of a presently preferred shape of the bottom of themagnet retaining groove 24. Since the lens 14 is transparent, the groove14, and anything contained in it, such as the magnets, will be visibleto onlookers. In order to be cosmetically pleasing, it may be desirablethat the magnets be hidden. This can be accomplished by filling thegroove with an opaque filler material or potting compound, such as, forexample, an epoxy filling 26 containing a colorant, and holding themagnets away from the bottom of the groove while the filler is curing.In the preferred embodiment of the invention, the magnets are held awayfrom the bottom of groove 24 by two shoulders 27. For clarity, theshoulders in FIGS. 7 and 8 are exaggerated (and not shown in FIGS. 2-5).Only a very small clearance is needed between the magnets and the bottomof the groove to allow the epoxy to hide the magnets from onlookers,perhaps 0.002″ will be adequate. The actual clearance needed will dependon the opacity of the epoxy. Also, the magnets are preferably a loosefit in the groove, and the filler material will flow around the sides ofthe magnets, helping to hold the magnets in the groove. The fillermaterial on the sides of the magnets is not shown in the drawings. Asmentioned above, for illustrative purposes, the magnets can be seen inFIGS. 1 and 9, even though in the presently preferred embodiment of theinvention only a circular colored stripe will actually be visible to anonlooker.

Rear lens 15 is held by rear ring 20, and the combination is coupled tothe front ring 19 through an elastomeric bellows 21, which allows therear ring to move with respect to the front ring. A thin membrane oftransparent distensible plastic film 22, such as saran, is attached tothe rear of the front ring, between it and the bellows. For purposes ofconvenience, the front ring may be referred to as a membrane supportmember or structure. The space between the film and the rear lens isfilled with a clear liquid 16, such as Dow-Corning DC-705 silicone fluid[which liquid (and the film) forms the liquid lens referred to above].The clear liquid 16 is retained between the rear lens 15 and the film 22by the elastomeric bellows 21.

A leaf hinge 23 couples the front and rear rings together at a pointapproximately opposite link 13. For explanatory clarity, the leaf hinge23 is shown scabbed onto the circumference of the rings, but inpractice, appearance and style may possibly dictate that the hinge beinset or otherwise partially or wholly hidden.

FIGS. 3 and 4 are fragmentary sectional views of the right lens unit 10taken near the location of the bridge 12. FIG. 3 shows the lens unitadjusted for distance viewing, and FIG. 4 shows the lens unit adjustedfor near viewing. The difference is that in FIG. 3, the link 13 isextended so that rear ring 20 is further from front ring 19, as comparedwith FIG. 4 where the link 13 is retracted and rear ring 20 is closer tofront ring 19, both distances being measured near the bridge. As link 13moves (in response to the user moving slider 30), the rings experiencerelative rotation (i.e., a clamshell type of motion) about a line nearleaf hinge 23.

For purposes of explanation, the rear lens, the filling liquid, and thefilm are assumed to have approximately the same index of refraction,although this is not an essential requirement. The preferred liquid,Dow-Corning DC-705, one of the preferred lens materials, polycarbonate,and the preferred film, saran, all have indices of refraction about1.58, and thus satisfy this preference. It is preferred that the frontsurface of the film 22 have a small positive optical power when thefocus module is set for distance viewing, for example, +1 diopter. Thereason for this last preference is that the actuating mechanismdescribed in U.S. Pat. No. 7,008,054 is capable of exerting force inonly one direction, and if an actuator of that type is used, an externalrestoring force is required to return the system to its distanceposition. Positive film curvature (which implies tension in the film)can be used to supply at least a part of the needed restoring force. Thebellows 21 and/or leaf hinge 23 can each also provide part of the neededforce

If the rearmost (i.e., exterior) surface of the rear lens has a negativecurvature amounting to an optical power of −1 diopter, the focus moduleas a whole, when in the position illustrated in FIG. 3, will have a netoptical power of zero (the +1 diopter optical power of the film surfacebalancing out the −1 diopter optical power of the rear surface). Notethat if the rear lens and the filling liquid have the same index ofrefraction, the interface between them has no optical effect, and theoptical power of the combination is equal to the sum of the powers ofthe two exterior surfaces. If the refractive indexes are not the same,the optical power at the interface may need to be taken intoconsideration.

When the link 13 is retracted toward the position shown in FIG. 4, theliquid will cause the film to bulge forward, increasing the opticalpower at its bulged surface, and thereby increasing the net opticalpower of the focus module. If the free area of the film is circular, asis preferred, the additional optical power will be spherical.

If, as set out in the example described above, the focus module has anet zero optical power when adjusted to the distance position, the frontlens would preferably be made to contain the intended user's actualdistance refractive demand, including both its spherical and cylindricalcomponents (and possibly prism). If the focus module were constructed tohave a distance optical power other than zero, say, for example, +2diopters of spherical power, then the front lens would preferably befabricated with the intended user's prescription, less 2 diopters ofsphere.

The term “detachable”, referring to the front lens, is intended to meanthat the front lens is removable from the focus module by the wearerwithout the use of tools. Front lens removal may be desired for a numberof reasons, including cleaning, or for replacement with tinted lenses toachieve sun protection. The front lenses of a pair of spectacles may beseparate items, as shown, or they may be fastened together by a bridgeof their own. They may be attached to the focus module by magnets, asillustrated, or by spring clips or other means. Even bayonet typeconnections may be used, if desired.

Referring now to FIG. 5, it will be noted that the section of thebellows 21 shown does not have the shape of a bellows, as it does in,e.g., FIG. 3. At or near the leaf hinge 23, instead of having a bellowsshape, the bellows 21 is preferably in the form of a solid piece ofrubber. The reason for this is to make it easier to fill the lens unitwith liquid. Since there is little or no relative motion between therings near the leaf hinge, no bellows action is needed, and making thesection solid is convenient.

To fill a lens unit, the needle of a hypodermic syringe filled withfilling liquid is inserted through the hole 25 in leaf hinge 23, andalso through the rubber at that section. Liquid can then be pumped intothe lens unit interior, and air correspondingly removed, until the lensunit is completely full. It is preferred that a pencil point, orotherwise non-coring needle, be used so that when the needle is removed,the hole will seal.

When in use, as described above, membrane 22 moves with respect to thefront lens 14 as the focus of the spectacles is adjusted. This motionwould cause the air pressure between the liquid lens and the front lensto vary if the space between them were sealed. It will be recognizedthat an increase in air pressure (as would occur when ring 20 is movedcloser to the membrane) might dislodge the front lens from the focusunit, or possibly cause other undesirable effects. Accordingly, it isdesirable that a purposeful air leak exist between the front lens andthe focus module. In the presently preferred embodiment of theinvention, this leak is achieved by having the magnets 18 protrudeslightly above the top of the groove 24 and epoxy filling 26. Hence,when the front lens is in place, there will be a small gap between thefront lens and the front ring 19 that allows air to pass.

One important class of users of the present invention is expected to beairline pilots. While extremely unlikely, portions of the outer skin ofairliners have been known to detach in flight at high altitude. If suchwere to happen, pressurization in the cabin could fail suddenly, and thepressure around a pilot could suddenly drop. If a front lens were todetach under such conditions, obvious problems could result. For airlinepilots, therefore, the gap between the front lens and the front ringmentioned in the previous paragraph should be adequately sized to permitsufficient airflow to assure that the air pressure on the rear of thefront lens will drop rapidly enough under sudden cabin decompressionconditions to assure that the front lenses are not dislodged.

FIG. 9 depicts a front view of a lens 14. The lens shape is purposelymade obviously non-symmetrical by, for example, including a tab 30, sothat a user will not inadvertently attach a right front lens to the leftside of the spectacles, and vice versa. The general shape of the lensaway from tab 30 is shown circular in the figure, but it will berecognized that any convenient shape could be used, as dictated byfashion, or other factors.

1. Variable focus spectacles comprised of: a pair of focus units, eachincluding a first fixed lens having a fixed optical power and a liquidlens having an adjustable optical power, the optical power of thecombination of said first fixed lens and said liquid lens beingadjustable between a first predetermined optical power and a secondpredetermined optical power, said focus units also each including a rimhaving a magnetizable front face; a bridge holding said focus units inspaced relationship; and a pair of second fixed lenses, each detachablyheld to a respective one of said focus units by a plurality of magnetsembedded in the rear surface of each of said second fixed lenses, saidmagnets magnetically engaging the magnetizable front faces of said rims,said second fixed lenses having optical powers, including sphericaland/or astigmatic and/or prismatic optical powers as required, suchthat, when added to said first predetermined optical power, theresultants equal the required far viewing corrections applicable to eacheye of a specific person.
 2. Variable focus spectacles as recited inclaim 1 and further including an actuator for adjusting the opticalpowers of said focus units.
 3. Variable focus spectacles as recited inclaim 1 wherein said first predetermined optical power is about zerodiopters.
 4. Variable focus spectacles as recited in claim 1 whereinsaid pluralities of magnets are held in grooves in the rear surfaces ofsaid second fixed lenses.
 5. Variable focus spectacles as recited inclaim 4 wherein said pluralities of magnets are held in said grooves bya colored filler.
 6. A process for fabricating variable focus spectaclescomprising: providing a pair of focus units, each including a firstfixed lens having a fixed optical power and a liquid lens having anadjustable optical power, the optical power of the combination of saidfirst fixed lens and said liquid lens being adjustable between a firstpredetermined optical power and a second predetermined optical power,said focus units also each including a rim having a magnetizable frontface; fastening said focus units together with a bridge between them;providing a pair of finished ophthalmic lens blanks each having frontand rear surfaces, said finished ophthalmic lens blanks having opticalpowers, including spherical and/or astigmatic and/or prismatic powers asrequired, such that, when added to said first predetermined opticalpower, would equal the required far viewing corrections applicable toeach eye of a specific person; fabricating a pair of second fixed lensesfrom said finished ophthalmic lens blanks; embedding a plurality ofmagnets in the rear surface of each of said second fixed lenses; andallowing said magnets embedded in each of said second fixed lenses toengage a respective one of said rims.
 7. A process for fabricatingvariable focus spectacles as recited in claim 6 wherein said firstpredetermined optical power is about zero diopters.